Winding mandrel for the production of reels of web material

ABSTRACT

The winding mandrel includes a substantially cylindrical wall with expandable members for the torsional locking of tubular winding cores. At least one portion of the wall is made of carbon fiber in a polymer resin matrix.

TECHNICAL FIELD

The present invention concerns the field of machines for the processingof paper and working of web materials, in particular but not exclusivelytissue paper.

STATE OF THE ART

In the production of reels of web material, in particular but notexclusively tissue paper, expandable winding mandrels are frequentlyused, fitted with one or more cores made of cardboard or otherlightweight material around which the required quantity of web materialis wound to form a log or roll. This roll, once the winding mandrel hasbeen removed, can be cut into smaller rolls with shorter axial lengthfor packaging and sale. In some cases, several axially aligned cores arefitted on the mandrel in order to simultaneously wind a plurality ofrolls with axial dimension equal to the dimension of the finished reel.

WO-03/074398 describes a machine for winding web material on windingmandrels of the type mentioned above.

U.S. Pat. No. 5,379,964, U.S. Pat. No. 6,454,204, EP-A-0322864 andEP-A-0850867 describe winding mandrels made at least partly of syntheticresin reinforced with carbon fiber. These mandrels have mechanicallocking systems operated in various ways. The locking elements thatprotrude from the mandrel to lock the winding core on it are controlledby internal members.

SUMMARY OF THE INVENTION

The invention relates to the production of expandable winding mandrelsof the type described above which are particularly efficient andreliable, resistant to wear and suitable for securely retaining andlocking the winding cores during the winding process. According to someembodiments, the invention proposes mandrels which reduce the weight androtation inertia, which provide good rigidity, robustness and resistanceto wear, and high critical speeds.

Substantially, according to a first embodiment, a winding mandrel isprovided for the production of reels of web material with a wall made atleast partly of carbon fibers, for example by winding continuous fibersor filaments in a resin matrix which then undergoes polymerizationand/or crosslinking. Expandable mechanical or pneumatic members areprovided along the mandrel wall to torsionally and axially lock thetubular cores on the mandrel.

In practical embodiments, according to the invention the elements thatlock the winding core on the mandrel are deformable, preferablyelastically, under the effect of the pressure of a fluid, preferablyair. In this way, when the mandrel is not operating, the expandablelocking members are preferably fully retracted in respective seats anddo not protrude from the outer surface of the cylindrical wall of themandrel. In this way said members do not interfere with insertion orextraction of the winding cores, reducing wear and at the same timefacilitating the insertion and extraction operations. Under the pressureof the (liquid or gaseous) fluid the expandable members deform,protruding from the outer cylindrical surface of the mandrel wall.Substantially, the deformable elements themselves, under the pressure ofthe fluid, form the member that cooperates with the core, locking it onthe mandrel. In other words, the expandable member swells due to theeffect of the fluid under pressure and protrudes from the surface of themandrel, pressing with a portion against the inner surface of thetubular winding core fitted on the mandrel.

In some embodiments the expandable members comprise a plurality ofexpandable elements, preferably pneumatic, which expand radiallyoutwards by delivering a fluid under pressure, for example andpreferably air. The fluid under pressure is delivered for example bymeans of a longitudinal duct which extends along at least a portion ofthe inner cavity of the mandrel and has a valve at one end of themandrel.

In some preferred embodiments of the invention, at least one insert isarranged along the mandrel, connected to the longitudinal duct fordistribution of the fluid under pressure, extending inside saidsubstantially cylindrical wall for at least a portion of the axiallength of the mandrel. Preferably, the insert comprises at least oneseat for an expandable pneumatic element, in fluid connection with saidlongitudinal duct. Preferably several inserts are provided distributedalong the axial length of the mandrel. In preferred embodiments of theinvention, each insert has at least two seats and preferably three seatsfor respective pneumatic expandable elements, angularly staggered withrespect to one another, preferably at a constant angular pitch betweenone seat and the other.

In some preferred embodiments of the invention, the substantiallycylindrical wall is formed of a plurality of tubular portions made ofcarbon fiber and one or more inserts; said tubular portions areinterconnected by said inserts, hence the outer surface of the mandrelis formed partly of the inserts, which can be made of metal, for examplea lightweight metal such as aluminum or its alloys.

In some preferred embodiments of the invention the outer surface of themandrel, formed of tubular portions made of carbon fiber and one or moreinserts, is covered with a metal or ceramic coating measuring a fewtenths of a millimeter (for example 0.3 mm). In this way it is possibleto remedy problems connected with abrasion of the core, generally madeof cardboard, on the outer surface of the mandrel. Due to thenon-uniformity of the mandrel component material (fiber+insert made ofaluminum or other material), it may be necessary to resort to anintermediate coating made of a material that effectively “bonds” on bothmaterials of the mandrel. The intermediate coating is then covered withthe material which will in turn be ground. This solution permitstrouble-free grinding of the entire mandrel as the mandrel is ground ona uniform material. Obviously the finished mandrel will not have thecoating on the expandable areas (i.e. on the expandable elastic walls).In practice, during construction of the mandrel a “plug” can be providedon these areas before applying the metal/ceramic material. Subsequentlythe metal/ceramic coating is applied, the mandrel is ground and lastlythe “plug” is removed, thus obtaining a mandrel formed of tubular carbonfiber portions and metal inserts, with a continuous ground metal/ceramiccoating, except for the expandable areas.

Preferably, the inserts are provided with means of connection orinterface to connect the inserts to the carbon fiber tubular portions.In some embodiments each of said inserts can have a substantiallycylindrical surface which defines, with outer surfaces of said carbonfiber tubular portions, the outer surface of the mandrel. Adjacent tosaid substantially cylindrical surface, frustoconical surfaces can beprovided for connection to the tubular portions connected to therespective insert. The carbon fiber tubular portions will have,internally, complementary frustoconical surfaces thus obtainingreciprocal coupling between the inserts and the carbon fiber tubularportions. Alternatively, to provide the connection between the tubularportions and the respective insert it is possible to use cylindricalsurfaces with a grooving, for example in the order of 0.2 mm, to enhanceadhesion between the fiber tubular portions and the inserts via the useof glue. In this configuration there is a negligible reduction in theresistance to force/tension transmitted between the two materials of thetubular portions and insert respectively during normal use of themandrel, but great construction simplification of the portion of fibertube is obtained as it does not require complex machining to obtain afrustoconical form. The tubular portion is then fitted inside and joinedby means of gluing.

Preferably the inserts comprise a central body, in which the seats forthe expandable members are provided, and axial ends each forming aninterface surface to attach said insert to the respective tubularportions.

In some embodiments, each insert has an axial through seat, inside whicha cylindrical member is housed, provided with an axial hole throughwhich said longitudinal duct passes. The longitudinal duct has, at eachinsert, at least one outlet for the fluid under pressure. Thecylindrical member is axially attached to the longitudinal duct andforms passages for supplying the fluid under pressure coming out of saidat least one outlet towards distribution channels formed in the insertand in fluid communication with the expandable elements.

In some embodiments the distribution channels comprise a ring-shapedgroove and substantially radial passages extending from said ring-shapedgroove towards said cavities containing the expandable elements.

In some embodiments the pneumatic expandable elements are formed ofvolumes of fluid under pressure, at least partially delimited by adeformable diaphragm or wall, preferably an elastically deformable one.The deformable wall can be made of natural or synthetic rubber, or otherelastically deformable material having suitable characteristics ofmechanical resistance and elastic deformability.

Further possible features and embodiments of the invention are set forthin the attached claims and will be described in greater detail belowwith reference to some embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by following the description andthe accompanying drawing, which shows practical non-limiting embodimentsof the invention. More specifically, in the drawing:

FIG. 1 shows an axonometric view of a mandrel according to the inventionin one embodiment;

FIGS. 2 and 3 show longitudinal sections of the ends of the mandrel ofFIG. 1;

FIGS. 2A and 3A show longitudinal sections of the ends of the mandrel ina modified embodiment;

FIG. 4 shows a longitudinal section of an intermediate portion of themandrel of FIG. 1 provided with inserts comprising expandable pneumaticelements;

FIG. 5 shows an enlargement of a portion of FIG. 4;

FIG. 5A shows an enlargement similar to that of FIG. 4, with partsremoved, in a different embodiment;

FIG. 6 is a section according to VI-VI of FIG. 5;

FIG. 6A is a section according to A-A of FIG. 5A;

FIG. 7 is a view according to VII-VII of FIG. 5;

FIG. 8 is an enlargement of an insert with expandable pneumatic elementsin longitudinal section in a modified embodiment of the invention;

FIG. 9 is a longitudinal section of an intermediate portion of a mandrelwith the inserts of FIG. 8.

DETAILED DISCLOSURE OF EMBODIMENTS OF THE INVENTION

FIG. 1 shows schematically a mandrel made according to the invention andindicated overall by the number 1. The mandrel has an intermediate part3 and two end portions 5 and 7 shown in the enlargements of FIGS. 2 and3. Along the portion 3 inserts 9 are arranged provided with expandablepneumatic elements, described below in greater detail.

In some embodiments, the ends 5 and 7 are made of metal, for examplealuminum.

In a preferred embodiment of the invention, shown in FIGS. 2A and 3A,each of the portions 5 and 7 can in turn consist of two elements: ahollow cylindrical pad, fitted to the final tubular portion made ofcarbon fiber, and a conical end part which is joined to the pad by meansof a coupling member, for example a pin, a screw, a set screw or othersimilar systems. In particular, FIG. 3A shows the end 7 in thisembodiment. 7A indicates the hollow cylindrical pad and 7B the taperedend part. 7C indicates a connection screw between the parts 7A and 7B.FIG. 2A shows the end 5, limited to the hollow cylindrical pad 5A, whichis provided with threaded holes 5C for fastening screws of a closingpart not shown. The advantages of this construction are:

-   -   possibility of accessing the inside of the tube also via the two        ends 5 and 7 (after removal of the tapered end);    -   possibility of disassembling the tapered end in the event of        breakage or failure thereof and replacing it without having to        replace the entire mandrel.

In the previous configuration the tapered end is one single pieceintegral with the tubular portion and therefore if one of the two ends 5or 7 breaks or fails, the entire mandrel would have to be discarded andreplaced with a new one.

The intermediate or central part 3 is made at least partly of carbonfiber in a polymer resin matrix. More specifically, in the embodimentshown in FIG. 1, with some details thereof shown in FIGS. 2 to 7, thecentral or intermediate part 3 of the mandrel consists of a plurality oftubular portions 11, each of which is made with a wall in carbon fiberin a polymer matrix. The various tubular portions 11 are interconnectedat the inserts 9, which in this embodiment constitute not only a housingfor the pneumatic expandable elements but also reciprocal connectionelements between the tubular portions 11 and have a substantiallycylindrical surface which forms, together with the cylindrical surfaceof the tubular portions 1, the outer surface of the mandrel 1.

Inside the mandrel 1, and for at least one portion of its axial length,a longitudinal duct 13 extends roughly coaxially with the cylindricalwall defined by the tubular portions 11 for delivery of a fluid underpressure, typically air, to expand the pneumatic expandable elementshoused in the single inserts 9. The longitudinal duct 13 has a terminalvalve 13A at the end 5 of the mandrel 1, via which the expandablepneumatic elements can be expanded or retracted by respectivelydelivering a fluid under pressure, or allowing the discharge thereof.

In this embodiment each insert 9 has a structure which is describedbelow with reference to FIG. 5 to 7. The insert has a central body 9A,in which seats are provided for the expandable pneumatic elementsdescribed below and from which axial ends 9B extend forming thereciprocal connection members between insert 9 and tubular portions 11.In some embodiments, the ends 9B have frustoconical outer surfaces 9Cdefining an interface with corresponding complementary frustoconicalsurfaces 11A provided on the respective two tubular portions 11 whichare connected to the insert 9. The frustoconical surfaces 9C have formand dimension such that the substantially cylindrical outer surface 11Bof each tubular portion 11 is substantially aligned with the outersurface 9D of the central body 9A of the insert 9 thus forming asubstantially cylindrical continuous wall of the mandrel 1. A smallring-shaped groove can be maintained between the edge of each tubularportion 11 and the central body 9A of the insert 9, as shown in thedrawing.

According to some embodiments, seats (three in the example of thedrawing) shown at 21 are provided inside the central body 9A, whichhouse the expandable pneumatic elements described below, forming thetorsional and axial engagement members of the winding core with respectto the mandrel.

In the example shown, the three seats 21 are arranged angularlystaggered by a constant angle of 120°, but other arrangements arepossible, for example with a different number of seats or with anirregular arrangement, i.e. with the various seats having differentangular pitch.

Each seat 21 houses an expandable element 23 comprising an elasticallydeformable wall, for example made of rubber and provided with a lip 23Afor anchorage and sealing inside the seat 21.

As can be seen in particular in the view of FIG. 7, in plan view theexpandable element has a substantially rectangular shape elongated inthe axial direction of the mandrel, although other shapes of theexpandable element in question are not ruled out, for exampledevelopment in a circumferential direction greater than the developmentin the axial direction.

Each expandable element formed by the wall 23 is locked in therespective seat 21 by means of a flange 25 with substantiallyrectangular development (FIG. 7). Locking is obtained by means of a pairof screws 27.

A distribution channel 31 leads into each seat 21, connecting the volumedefined between the bottom of the seat 21 on one side and the deformablewall forming the pneumatic expandable element 23 on the other with thelongitudinal duct 13. In some embodiments this connection is obtained byinterposing a cylindrical member 33 inserted coaxially and around thelongitudinal duct 13 and inside an axial hole 9E of the insert 9. Thecylindrical member 33 has a plurality of outlets shown at 35 for thefluid under pressure, which can be in positions angularly correspondingto the positions of the ducts 31. In some embodiments the outlets 35lead at one end into a ring-shaped groove 37 in the axial hole of thecylindrical member 33 and on the opposite side into a ring-shaped groove39 provided in the inner surface of the hole 9E of the body 9A of theinsert 9. With this arrangement, the angular position of the cylindricalmember 33 can be made independent of the angular position of the seatsfor the pneumatic expandable elements, since the ring-shaped grooves 37and 39 nevertheless guarantee a flow connection.

In some embodiments, the cylindrical member 33 has seal gaskets 41 and43 between the cylindrical member 33 and the longitudinal duct 13 on theone side and between the cylindrical member 33 and the inner surface ofthe hole 9E of the insert 9 on the other.

In some embodiments, the cylindrical member 33 is axially secured byforcing or other suitable manner inside the hole 9E of the body 9A ofthe insert 9. In some embodiments the cylindrical body 33 is in turnaxially secured to the longitudinal duct 13 by means of a diameter pin45. In this way a reciprocal positioning is obtained between thelongitudinal duct 13 and the inserts 9. This reciprocal positioning canalso be obtained with other forms of attachment between the parts 13, 33and 9.

The inserts 9 are arranged in an adequate number along the axial lengthof the mandrel 1, according to the longitudinal dimensions of themandrel and other operating requirements. In the embodiment shown, eachinsert 9 has three expandable pneumatic elements arranged at 120° fromone another, but as mentioned above, the number of the latter can vary.For example four or two of said expandable elements can be provided oneach insert 9. The arrangement of the inserts around the axis of themandrel 1 is such that the pneumatic expandable elements are arranged invarious angular positions around the development of the mandrel thusobtaining an effective torsional and axial locking effect of the windingcores on the respective mandrel. By way of example only, FIG. 5 shows aportion of a tubular core A fitted on the mandrel 1, which can be lockedon the latter both axially and torsionally by introducing a fluid underpressure into the longitudinal duct 13 to cause radial expansion of thepneumatic expandable elements 23.

With the configuration described so far, an extremely lightweightmandrel is obtained with a high level of rigidity due to the use ofcarbon fiber. Using inserts 9 which form ring-shaped portions of theouter surface of the mandrel, and which join aligned tubular portions 11made of carbon fiber, the further advantage is achieved of obtaining allthe expandable elements and members connected therewith in an area whichdoes not require any machining of the walls made of carbon fiber (anotoriously fragile material) which form the tubular portions 11. Thisguarantees a high resistance of the mandrel by eliminating points wherestress, defects and possible delaminations of the fiber layers areconcentrated.

Furthermore, the presence of the inserts 9, advantageously made ofmetal, for example aluminum (at least for the body 9A and the ends 9B,while the cylindrical member 33 could preferably be made of plastic)makes balancing of the mandrel much quicker, simpler and more effective.In fact, these members must be appropriately balanced to prevent themvibrating during use. The presence of metal areas distributed along theaxial length of the mandrel, consisting of the various inserts 9, makesit possible to remove or add material, for example by drilling thealuminum block forming the body 9A of the single insert and if necessaryinserting into the hole thus obtained counterweights made of differentmaterials, with higher density than the aluminum.

FIGS. 5A and 6A show a modified embodiment, in longitudinal and crosssection respectively. These figures show only the central body of theinsert 9. Identical numbers indicate parts identical or equivalent tothose of the embodiment example illustrated in FIGS. 5 and 6. The ends9B of the body 9A have in this case a substantially cylindrical surfaceprovided preferably with one or more grooves 9S with depth of a fewtenths of a millimeter, to obtain a coupling, if necessary by gluing,with the substantially cylindrical inner surface of the tubular portions11. FIG. 5A also shows a possible coating R made of ceramic and/or metalwhich covers the entire outer surface of the mandrel with the exceptionof the area in which the expandable elements are provided. This coatingis applied on the fully assembled mandrel, completed with inner elementsof the inserts 9, which are omitted here for the sake of clarity of thedrawing. The coating can also be provided in the remaining embodiments.

FIGS. 8 and 9 show a modified embodiment of the invention. Identicalnumbers indicate identical or equivalent parts with respect to thosedescribed above with reference to FIG. 1 to 7. In this embodiment, thecentral part 3 of the mandrel 1 is formed of one single tubular body ortubular portion 11 made of carbon fiber. This tube 11 made of carbonfiber, similarly to the tubular portions 11 of the previous embodiments,can be produced using known techniques for winding of fibers orcontinuous filaments around a forming mandrel, in which the fibers orfilaments are fed together to a polymerisable resin to form acylindrical wall around the forming mandrel. The wall thus obtainedsubsequently undergoes polymerisation and/or crosslinking of the resinmatrix.

Inside the cylindrical hollow body formed by the carbon fiber wall 11, alongitudinal duct, again indicated by 13, for the delivery of a fluidunder pressure, typically air, extends for at least a portion of theaxial length of the mandrel 1. As in the previous example, this duct 13has an end valve 13A for delivery of fluid under pressure or fordischarge of the fluid to the outside.

Along the axial length of the mandrel 1, inside the cavity 11B formed bythe carbon fiber wall 11, inserts 109 are arranged, forming housingseats for pneumatic expandable elements described below with particularreference to FIG. 8. The positioning of the inserts 109 and the axialdistribution thereof along the mandrel 1 are chosen according tooperating and construction requirements.

In some embodiments the insert 109 has a body 109A (FIG. 8), in whichradial seats 121 are provided where a cylinder 122 is inserted with itsaxis in a radial direction and having channels 123 in fluid connectionwith the longitudinal duct 13 which passes through a central diameterhole of the cylinder 122. At the ends thereof the cylinder 122 isattached, for example by means of two threads, to two sleeves 125locking respective pneumatically expandable elements 127 substantiallyin the form of a cap formed of an elastically deformable material, forexample rubber. Between the pneumatically expandable element 127 and therespective end of the cylinder 122 a chamber or volume 129 is defined,in which fluid under pressure can be introduced via the duct 123 and theduct 13. Between each sleeve 125 and the seat 121 formed in the body109A of the insert 109 respective gaskets 131 are arranged. Similarly,between the body 109A of the insert 109 and the longitudinal duct 13,which passes through an axial hole of the body 109A of the insert 109,further seal gaskets 133 are arranged.

In an appropriate manner, each insert 109 is axially attached to thelongitudinal duct 13, for example via the use of a respective diameterpin 135 or set screws or other equivalent means.

As shown in particular in FIG. 8, each expandable element 127 is housedat least partially inside a respective hole 11F provided in thecylindrical wall 11 made of carbon fiber. This embodiment, therefore,requires machining by drilling of the carbon fiber component 11 formingthe central or intermediate part 3 of the mandrel 1, with consequentformation of stress concentration areas along the mandrel wall.Furthermore, balancing of the mandrel is more difficult due to the lackof metal surfaces accessible from the outside which can be machined tolighten the component.

The operation of the mandrel in this embodiment can be easily understoodfrom the above description. The core A (shown partially in FIG. 8) istorsionally and axially locked on the mandrel by expansion of theindividual pneumatic expandable elements 127 due to the delivery of afluid under pressure, typically air, through the longitudinal duct 13and the radial ducts 123. The core is released by discharging thepressure from these ducts.

It is understood that the drawing only shows one example provided as apractical demonstration of the invention, which can vary in the formsand arrangements without departing from the scope of the conceptunderlying the invention. Any reference numbers in the attached claimsare provided to facilitate reading of the claims with reference to thedescription and the drawing, and do not limit the protective scope ofthe claims.

1-23. (canceled)
 24. A winding mandrel for producing reels of webmaterial, comprising a substantially cylindrical wall with expandablemembers for torsionally locking tubular winding cores on said mandrel,wherein at least a portion of said wall is made of carbon fibers in apolymer resin matrix; said expandable members include a plurality ofexpandable elements that expand radially outwards of said substantiallycylindrical wall by delivery of a fluid under pressure thereto; aplurality of inserts are provided along an axial length of the mandrel,said inserts being connected to a longitudinal duct for the distributionof the fluid under pressure, wherein said duct extends inside saidsubstantially cylindrical wall for at least a part of the axial lengthof the mandrel; and each of said inserts comprises at least one seat foran expandable element, in fluid connection with said longitudinal duct.25. The winding mandrel according to claim 24, wherein said expandableelements are pneumatic expandable elements.
 26. The winding mandrelaccording to claim 25, wherein said fluid under pressure is air.
 27. Thewinding mandrel according to claim 24, wherein said expandable elementsare deformable due to said delivery of said fluid under pressure so asto protrude from said substantially cylindrical wall; and wherein inabsence of said fluid under pressure, said expandable elements areentirely retracted in respective seats so as to not protrude from anouter surface of said substantially cylindrical wall.
 28. The windingmandrel according to claim 24, wherein each of said inserts includes atleast two seats for corresponding expandable elements arranged inangularly staggered positions around an axis of the mandrel.
 29. Thewinding mandrel according to claim 24, wherein the substantiallycylindrical wall is composed of a plurality of tubular portions made ofcarbon fibers in a polymer resin matrix, and of one or more of saidinserts; said tubular portions being connected to one another by saidinserts.
 30. The winding mandrel according to claim 29, wherein each ofsaid inserts has a substantially cylindrical surface that defines,together with outer surfaces of said carbon fiber tubular portions, asubstantially cylindrical surface.
 31. The winding mandrel according toclaim 30, wherein said substantially cylindrical surface has asubstantially continuous coating.
 32. The mandrel according to claim 31,wherein said coating comprises at least one layer comprising metal orceramic.
 33. The winding mandrel according to claim 29, wherein each ofsaid inserts includes a central body containing said at least one seatfor the expandable elements and axial ends which each form aninterfacing surface for attaching said inserts to respective tubularportions.
 34. The winding mandrel according to claim 33, wherein saidaxial ends have an outer surface which is tapered or cylindrical, saidouter surface being grooved for anchorage of the tubular portions. 35.The winding mandrel according to claim 33, wherein said central body hasa substantially cylindrical outer surface provided with cavities forhousing said expandable elements.
 36. The expandable mandrel accordingto claim 24, wherein each of said inserts has an axial through cavity inwhich a cylindrical member is contained, with an axial hole for passageof said longitudinal duct; coinciding with each of said inserts, saidlongitudinal duct has at least one outlet for the fluid under pressure;and said cylindrical member is axially attached to the longitudinalduct, forming passages for the delivery of the fluid under pressurecoming from said at least one outlet into distribution channels formedin said inserts and in fluid connection with said expandable elements.37. The expandable mandrel according to claim 35, wherein each of saidinserts has an axial through cavity in which a cylindrical member iscontained, with an axial hole for passage of said longitudinal duct;coinciding with each of said inserts, said longitudinal duct has atleast one outlet for the fluid under pressure; and said cylindricalmember is axially attached to the longitudinal duct, forming passagesfor the delivery of the fluid under pressure coming from said at leastone outlet into distribution channels formed in said inserts and influid connection with said expandable elements; and said distributionchannels comprise a ring-shaped groove and substantially radial passagesextending from said ring-shaped groove towards said cavities for housingthe expandable elements.
 38. The winding mandrel according to claim 24,wherein said expandable elements are formed by volumes of fluid underpressure at least partially contained by a deformable diaphragm.
 39. Themandrel according to claim 38, wherein said deformable diaphragm is madeof an elastic material.
 40. The winding mandrel according to claim 35,wherein each of said cavities for each of said inserts contains anexpandable element comprising an elastically deformable wall with ananchorage and sealing lip, fixed in a respective one of said cavities bya locking flange that retains said anchorage and sealing lip inside agroove provided in a corresponding cavity.
 41. The winding mandrelaccording to claim 24, wherein said expandable elements are housedinside corresponding radial holes provided in the substantiallycylindrical wall made of carbon fibers in a polymer resin matrix anddefining said substantially cylindrical wall of the mandrel.
 42. Thewinding mandrel according to claim 24 comprising metal terminal ends, atleast one of said metal terminal ends being associated with means foractivating the expandable members.
 43. The winding mandrel according toclaim 42, wherein at least one of said metal terminal ends is made intwo parts, a first part attached irreversibly to the mandrel with ahollow body to allow access to inside of the mandrel, and a second partremovably attached to said first part.
 44. The winding mandrel accordingto claim 24, wherein said inserts are made of a metallic material.